This invention relates to sensing switches used in the general field of data processing and, more particularly, to switches for automatically sensing card-like forms such as checks, computer cards, or similar documents.
It is desirable to process a continuous stream of such documents and, therefore, it is desirable that a sensing switch be provided to count the documents. For example, the documents may be counted prior to their being photographed, endorsed, or otherwise processed.
The present invention relates to improvements in switches of the type exemplified in and protected by my prior U.S. Pat. Nos. 3,202,779, 3,461,255 and 3,912,890. All of the above-mentioned patents disclose sensing switches which generate electric signals responsive to a passage of documents as they move through a path of travel.
Two of these patents used a wheel which had three fingers or "flippers" which were equally spaced around the periphery. Each document that passed through the sensing area engaged the finger or flipper and indexed the wheel to cause it to move through a 120.degree. rotation. The problem with this type of sensor is that it is large and bulky. At the time, when the wheel sensor was made, miniaturization of equipment was not as important as it is today. Therefore, a large machine did not suffer too many penalties. Today, however, it is very difficult to sell a machine which is larger and more bulky than its competitor.
A third of my prior patents eliminated the wheel and thereby became more compact. However, it also depends upon gravity and, therefore, cannot be used in any orientation except the single one where gravity pulled the parts back to their normal position.
Beyond this, each of the switches in my earlier patents include design consideration which prevented the take-up rollers from being positioned as close to the output of the sensor as is possible with the subject invention. Thus, these closely positioned take-up rollers enable the present sensor to have a greatly reduced tendency to jam, which leads to looser manufacturing tolerances and, therefore, lower cost production. The freedom from jamming is further enhanced by the provision of a resilient guide finger for urging the document to follow a predetermined travel path which better leads into the take-up rollers.
Yet another consideration is the environment in which the sensor operates. As the documents feed through their travel path, lint tends to rub off and to build up a binding accumulation. The mechanical parts tend to bind and become restricted and the electrical contacts tend to become dirty due to the accumulaton of lint.
The invention solves these and similar problems by providing spring-biased actuator arms and by providing reed contacts sealed in glass.
Accordingly, an object of the invention is to provide new and improved document sensors. In this connection, an object is to provide sensors which operate in virtually any physical orientation. Here, an object is to provide a more jam-free operation.
Another object is to provide a more reliable document sensor. Here, an object is to provide a document sensor which is less adversely affected by an accumulation of any lint which may be rubbed off the documents. In particular, an object is to provide sensors which operate sealed contacts.
Still, another object of the invention is to provide highly reliable miniature document sensors.
According to an aspect of the present invention, switches are provided for sensing the passage of documents, such as a card, through an apparatus, especially one used in data processing. The sensing switch comprises an assembly which includes a base portion rigidly mounted on the apparatus and containing normally closed contacts sealed in glass. A linkage assembly mounted on the base portion includes a lower link and an upper link, the upper link serving as a sensing element which is moved by the document. A lower portion of the lower link is pivotally and resiliently mounted on the base portion of the switch. At its upper portion, the lower link has the sensing element pivotally and resiliently mounted thereon. In the initial position of the sensing switch, a toe of the sensing element is positioned to contact edges of documents, such as cards, which are part of a continuous stream of documents moving along a travel path in the apparatus.
Continuous movement of a document along the path drives the lower link of the sensing element away from the base portion, to open the contacts mounted in the base portion, for counting the document. A cam surface engages the sensing element to cause it to drop the arm from its engagement with the leading edge of the card to an engagement with the under surface of the card. Resilient means are provided between the sensing element and the lower link for biasing the sensing element against the under surface of the card, as it continues to move through the travel path. Associated resilient means are mounted on the base portion of the assembly to press the lead edge of the card and to retain it against a guide plate as it moves into the nip of take-up rollers at the output of the sensor.
If two cards enter the travel path in an overlapped relationship, with the upper card preceding the lower card, the arm goes through its cycle of operation for each leading edge thus counting, endorsing, or otherwise processing each of the two documents individually.